A First Look at Node-Level Curtailment of Renewable Energy and its Implications

Electricity grids are trying to meet their demand by using more renewable energy as they move towards decarbonization.As the amount of renewables in the grid increases, there are periods when renewable supply exceeds the demand or when excess supply cannot be transmitted to a different location to satisfy the demand due to grid congestion.Consequently, renewable generators often need to be curtailed so that they operate below their maximum capacity.Such curtailment represents unutilized "green" energy that could have replaced energy produced from non-renewable "brown" sources.While prior works have studied curtailment at the grid level, curtailment is a local phenomenon that occurs at the level of a generation node, where each node is a power plant at a specific location feeding the grid.A grid may consist of hundreds of nodes, but curtailment may only occur in some nodes and at some times.Hence, understanding curtailment at the node level is important to evaluate its potential for decarbonization.We study curtailment at the node level for the Texas grid operated by ERCOT, which consists of hundreds of nodes producing wind and solar energy.Using extensive node-level data for the year 2023, we show that curtailment is highly non-uniform and intermittent -20% of the nodes account for 77% of the total curtailed energy, while 70% of the nodes are curtailed for less than 10% of the year.We find that although wind curtailment is more prevalent, a greater fraction of solar generation is curtailed than wind.We also develop a method to identify the cause of curtailment from the Locational Marginal Price (LMP), showing that 74.3% of the time, curtailment in Texas is due to grid congestion.Overall, our analysis of node-level curtailment implies that while curtailment can potentially be forecasted in only a small fraction of the nodes, a considerable amount of curtailed energy can be utilized by adding demand adjacent to these nodes.